Observing conduit flow processes during Strombolian Eruptions using Transient Electromagnetics (TEM): a numerical and field approach

火山爆发是地球上可以看到的最迷人的景象之一。火山爆发对人类是好事也是坏事，减轻火山爆发的影响是一项重大的社会任务。除其他外，缓解战略涉及短期危机管理，包括火山爆发预警。在这方面最关键的是了解火山喷发之前的火山导管内部的过程。对岩浆在管道中的输送过程的现场观测仍然几乎是不可能的。到目前为止，几乎所有的测量都依赖于遥感技术，如地震学观测、倾斜测量或地面InSAR观测。导管在喷发前的所有过程都涉及气泡的成核和生长。在斯特隆波利火山爆发的情况下，这些气泡通常相当细长，长宽比远远大于1。它们被称为气体鼻涕虫。该提案的目标之一是探索瞬变电磁学（TEM）的潜力，以监测火山导管中通过喷发前最后100米的气体段塞的最终上升。电磁方法在火山环境中普遍表现出较高的潜力，这是由于岩浆、气体和寄主岩石之间的感应耦合和高电导率对比。通过使用高度复杂的三维瞬变电磁法正演模拟软件进行虚拟实验，我们将探索地下响应的敏感性，特别是考虑到真实地形和地下特征，如热液系统以及充满岩浆的管道，包括气段塞。我们将研究各种设置，包括不同的源/接收器配置对真实火山环境中透射电镜响应的影响。这将使我们能够确定在活火山爆发前使用瞬变电磁法记录的特征信号。为了做到这一点，我们将用自适应网格和复杂的地质建模工具扩展现有的软件，以正确地描述火山大厦，从而产生新的建模技术和地电磁学结果。利用意大利斯特龙博利火山现有的地球物理信息进行详细的灵敏度研究，我们将进行一组虚拟实验，以约束可能的测量配置，以优化斯特龙博利的现场实验。我们建议利用瞬变电磁法进行现场实验，以监测火山导管内的过程。这些瞬变电磁法测量结果将由使用照相机和多普勒雷达监测火山喷发来补充。结合这些数据，我们有望更好地限制段塞的上升，并为火山导管中气体段塞的上升建立基准数值模型，从而改善火山灾害的缓解。

Volcanic eruptions are one of the most fascinating spectacles that can be witnessed on Earth. They are boon and bane to mankind and mitigating the effects of volcanic eruptions is a major societal task. Among other things mitigation strategies involve short term crisis management including short notice eruption warnings. Most crucial in this regard is the understanding of processes inside volcanic conduits preceding an eruption. In situ observations of magma transport processes in the conduit are still nearly impossible. So far almost all measurements rely on remote sensing techniques like seismological observations, tilt measurements or ground based InSAR observations. All processes in the conduit prior to an eruption involve the nucleation and growth of bubbles. In case of strombolian eruptions these bubbles are usually quite elongated with a length to width ratio being much larger than 1. They are called gas slugs. One of the goals of this proposal is to explore the potential of transient electromagnetics (TEM) to monitor the final rise of such gas slugs in the volcanic conduit passing through the last 100 m prior to the eruptions. Electromagnetic methods in general show a high potential in volcanic environments due to inductive coupling and the high conductivity contrast between magma, gas and host rock. By running virtual experiments using a highly sophisticated three-dimensional TEM forward simulation software we will explore the sensitivity of the subsurface response taking especially into account real topography and subsurface features like hydrothermal systems as well as a magma filled conduit including a gas slug. We will investigate the effect of various setups including different source/receiver configurations on the TEM response in a realistic volcanic setting. This will allow us to determine characteristic signals that we would expect to record at an active volcano using TEM prior to an eruption. In order to do so, we will expand an existing software with an adaptive meshing and sophisticated geomodeling tools to properly describe the volcanic edifice leading to novel modeling techniques and results in geoelectromagnetics.Applying a detailed sensitivity study using geophysical information available for Stromboli volcano, Italy, we will carry out a set of virtual experiments to constrain possible measurement configurations to optimize a field experiment at Stromboli. We propose to carry out a field experiment using TEM for monitoring processes within the volcanic conduit. These TEM measurements will be complemented by monitoring the eruptions using cameras and Doppler radar. Combining those data hopefully enables us to better constrain slug rise and benchmark numerical models for the rise of gas slugs in volcanic conduits thereby improving volcanic hazard mitigation.